150 



Dr. Stenhouse on Ruhia munjista. 



|:i864. 



I. '3435 grm. pupmeine gave '8230 grm. carbonic acid and '1240 grm. 

 of water. 



II. -340 grm. purpureine gave '813 grm. carbonic acid and '123 grm. of 

 water. 



III. '336 grm. purpureine gave •01552 grm. nitrogen. 



IV. *535 grm. purpureine gave "02453 grm. nitrogen. 







Theory. 



1. 



II. 



III. 



IV. 



^66 



= 396 



65-13 



65-36 



65-22 









= 24 



3-95 



4-01 



4-02 







N, 



= 28 



4-60 







4-62 



4-58 



0,0 



= 160 



608 



26-32 

 100-00 











The formula therefore appears to be H^^ O^o ?. 



Nitropurpureine. 



When purpureine is dissolved in a small quantity of moderately strong 

 nitric acid, spec, grav. about 1-35, and heated to 100° C, it gives oif red 

 fumes, and on being allowed to cool, a substance senarates in magnificent 

 scarlet prisms somewhat like chromate of silver, only of a brighter colour ; 

 it is quite insoluble in water, ether, and bisulphide of carbon, and very 

 shghtly soluble in spirit, but soluble in hot moderately strong nitric acid, 

 from which it separates on standing for a considerable time. If boiled with 

 strong nitric acid, it is slowly decomposed. When heated, it deflagrates : 

 from this circumstance, and considering its mode of formation, it is evidently 

 a nitro-substitution compound ; I have therefore called it nitropurpureine. 



Owing to the small quantity which I have hitherto been able to procure, 

 I have not yet determined the composition of this beautiful body, which is 

 finer in appearance than any of the derivatives from madder I have as yet 

 met with. 



Action of Ammonia on Alizarine. 

 The alizarine which was employed for the subjoined experiments was 

 obtained by extracting Professor E. Kopp's so-called green alizarine* with 

 bisulphide of carbon. It yields only about 15 per cent, of orange-red ali- 

 zarine. This was crystalhzed three times out of spirit, from which it usually 

 separates as a deep-orange-coloured crystalline powder. Unfortunately this 

 alizarine still contains a quantity of purpurine, from which it is impossible 

 to purify it either by crystallization or sublimation. Accordingly, when 

 treated with ammonia by the method already described for purpurine, 

 while it yields a substance analogous to purpureine, the product is impure, 

 being contaminated with purpureine. This mixture has been examined by 

 my friend Professor Stokes, who finds that it contains purpureine, derived 

 from the purpurine present as an impurity in the alizarine employed, and 

 another substance very like alizarine - in its optical properties, probably 

 a new substance (alizareine), bearing the same relation to alizarine that 



* I am also indebted to Professor Calvert for the " green alizarine." 



